


on a knife's edge

by writedeku



Category: Assassination Classroom
Genre: After-Fight Fuck, Anal Sex, Based off season 2 episode 18, Basically, Hate Sex, M/M, Plot What Plot/Porn Without Plot, There is some plot though, They're 15 so underage, heh, i mean analysis of the fight, lots of cool words, school sex
Language: English
Status: Completed
Published: 2017-06-20
Updated: 2017-06-20
Packaged: 2018-11-16 11:13:53
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 2,624
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11251962
Author URL: https://archiveofourown.org/users/writedeku/pseuds/writedeku
Summary: Like a comet hurtling to Earth, Nagisa appears behind the four of them he sent and cuts them down as if they were nothing but flies. He turns to look exactly where Karma is, his eyes alight, on fire, burning with that unholy blue the same way it did when Takaoka broke all those glass vials. Karma watches from his position in the trees, stunned nearly senseless, rock hard in his pants.





	on a knife's edge

**Author's Note:**

> Sex, sex and more sex! This time featuring Karma and Nagisa, the assassin's power couple.

The war game Koro-sensei had devised was devastatingly simple and beautiful in it’s nature. As he could hear the sound of gunfire in the distance, he imagined that they were killing actual, real people, and that where they are now is not the backyard of their schoolhouse but a beautiful, wonderful assassination floor. While Karma knows he has a mission to protect on behalf of the people who are dying for him, he cannot help but want, almost desperately, to fight. Not just anyone in particular, which has always been his habit, oh, bloodsoaked fists and the sound of crunching, wrenching bone has always been his theme, he wants in this moment to fight a small boy with eyes darker than his soul. Karma has known Nagisa ever since they were first years and he was too big for his britches. Already then, the small, petite boy was cute and disarmingly so. Everything about him spoke of first glances and forgetfulness, as though he was so inconsequential, your eyes would just pass right over him. Karma gave much thought to his lackey back then, afraid, for some reason, like one would be of a small, small spider.  

He shakes off the nostalgia and sends forth his squad, aching, desperate to emerge victorious for his mission. Nagisa used to be never be an obstacle in the way. Now, he is a beautiful obstacle, no longer inconsequential and cute. Nagisa is the one thing that stands between him and victory, which is a sensation Karma is so unused to that he cannot understand. He thinks back to the night Takaoka and Nagisa dueled it out on the Helipad, and the harsh, cold, devastatingly cruel glance of Nagisa’s ice-blue eyes. Before, they’d never been ice, they’d been sky-blue or sea-blue, if he was feeling generous. The kind of blue that made you sleepily peaceful. But that look in Nagisa’s eyes had sent feelings of pure arousal coursing through him like a hot blade, and he almost buckled and fell to his knees with the weight of it all.

“I’ve got eyes on the flag,” Nakamura says, her tone joyous and full of self-serving victory- and then, from out of nowhere, like a comet hurtling to Earth, Nagisa appears behind the four of them he sent and cuts them down as if they were nothing but flies. He turns to look exactly where Karma is, his eyes alight, on fire, burning with that unholy blue the same way it did when Takaoka broke all those glass vials. Karma watches from his position in the trees, stunned nearly senseless, rock hard in his pants. 

“No,” Nagisa says, his words vindictive and vicious. “You don’t.” 

Karma knows now, that this is the best time he’ll ever have to sock Nagisa in the jaw. He palms his erection in his pants and straightens, hoping neatly off his perch. 

He talks as he walks towards Nagisa. His beautiful blade. His little dagger. Somehow, he manages to distract himself from the fact that Nagisa has already moved from the scene of the massacre, and is gone, even his presence has disappeared to a missable drizzle. What Karma has chosen to fight is not a boy, nor an assassin, he has chosen to fight a force of nature itself. His blood sings.  

He is surprised when Nagisa consents to his offer of a one-on-one fight. He knows too, that Nagisa is not doing so because he underestimates his abilities but because he stands in awe of them. The only way to convince the class that a true fight has been waged and a true winner has been declared would be to fight one another with all their emotions flaring about, wildly running amok, and meeting where their fists do.  

His fist meets Nagisa’s face, he can feel the skin bruising beneath it, hear Nagisa’s cry of pain as he does. The friction rubbing against his still-strong erection doesn’t damper the mood. Nagisa retaliates with a particularly strong one of his, his eyes hard and unwavering, and if they didn’t have an audience, Karma would moan. Back and forth, back and forth they go, Nagisa taking the most damage, of course. They fall on one another and in the meeting of his skin on flesh he can hear Nagisa saying, “let me try to save him, so I don’t become like the  _ shinigami _ .”

_ Let me try to save him, so I don’t only become an assassin.  _

_ I will try, because I can use this power to help someone! _

_ Listen, Karma! We can’t follow Koro-sensei’s footsteps. Not like this!  _

_ Karma! _

_ Karma! _

_Karma!_  

He hopes Nagisa understands what he’s trying to say too, with every cruel, malicious kick to the stomach. When he finally lands the axe kick and Nagisa goes soft and limp in his hands, and falls to the ground, Karma’s chest is heaving but he’s never felt lighter. They’ve met in the middle, where they were always supposed to meet. 

And yet, somehow, Karma finds himself on his back, his eyes staring at the powder blue of the sky. Nagisa’s eyes, he thinks blearily, and realises just how deprived of oxygen he is. The smaller boy is writhing on top of him, having got him in the perfect choke, and as he does, Karma can feel the fact that he is hard too, rubbing against his thigh. He chooses to forgo the blade in the back. Even after they’ve parted and he’s surrendered, he can still feel Nagisa’s breath on his neck, the hardness on his thigh, and just how close he’d been to climax. 

“Nagisa,” he says, pulling the smaller boy up to him, an honest smile on his face as for the first time, in a long time, he feels wonderfully, irrevocably, alive. “Let’s drop the formalities.” 

The boy has lost the fire in his eyes. “Ah, that’d be weird,” Nagisa rubs the back of his head but smiles anyway. “But okay, Karma.”

He gets the sentiment again through their touching hands.

_ Anything for you, Akabane Karma.  _

He hisses between clenched teeth. 

* * *

 

Karma thinks it’s not a miracle that Nagisa has the same presence of mind to stay back after the class has gone- they seem to operate on the same wavelength. Both say they want to talk to each other when they are questioned, and the students don’t doubt it. After the fight, it would be only natural to talk about it, right? 

Karma refuses a bandaid for his split knuckles, relishing instead in the way it looks against his pale skin. He looks up as Nagisa enters the classroom and sits in the seat next to him. They look at each other, form words, and discard them just as quickly. 

“You were hard,” Nagisa finally says after they continue this dance for two or so minutes. Karma stops prodding at a bruise on his arm. “When we fought.”

“So were you,” Karma whispers, his eyes seductive and low. Their delicate balance that they’ve established hangs treacherously on a knife’s edge. “What are you going do about it?”

Nagisa looks at him in the eye, and oh, that look Karma loves so much is back and blazing. He can feel himself getting hard again, just from the look of his little viper. Nagisa stands, and then Karma does too, backing away from his presence until his back hits the wall and Nagisa is staring at him intently. 

“I hope you don’t mind,” Nagisa whispers. Karma’s going to get a hate, emotion fueled fuck, he can tell. “What I do about it.”

“I don’t think I will,” Karma smirks. Nagisa, little, easily flustered Nagisa- what an act he puts on, an unbelievable, overwhelming act. Nagisa is only blushy and unreliable in the instances which don’t matter. But the times that it does, he is unparalleled in his ability to rise to the occasion and take it with greedy, grabbing fists. 

Nagisa grins too, a hint of teeth showing in the rapidly darkening classroom as the sun sets. “That’s good,” his voice is now just a breath on Karma’s lips, and then he’s pressing his lips to his, one hand firmly on his tie, the other on his waist. Karma groans into the kiss, because  _ finally  _ he’s getting what he wants. His little viper, all coiled for the taking. 

Karma kisses back hungrily, hands sliding greedily over Nagisa’s body,undoing his waistcoat with practised hands, untucking his shirt and pressing his hands to the bare skin that’s been unveiled to him. His fingers slide over the bumps of muscle on his chest, stopping to tweak at a nipple, causing Nagisa to jerk out of the kiss and moan into his neck. Fluidly, he switches from attacking his mouth to kissing his way down Karma’s neck, biting down at random instances and sucking. Karma’s erection now strains against his pants, and it’s overwhelming.

He pushes Nagisa back to properly strip him of his clothes, lying him on a desk and undoing one button by one button as slow as sin, tonguing the bare skin that’s revealed as the fabric falls away. It reveals purple bruises from his knees and his fists during his fight. Karma digs his fingers into them and watches delightfully as Nagisa gasps and cries out and bucks his hips in the air, just as hard as he is. 

Karma undoes his belt with a smile and shucks his pants off, revealing a lovely bulge in a pair of dark grey underwear. He mouths at the bulge, making the wet spot increase and increase, until Nagisa grips him by the hair and says, “take it off, Karma.”

Karma gladly does. He strips off the fabric immediately and licks up Nagisa’s cock slowly from base to tip, watching it twitch beneath his ministrations. He licks around the base, mouths over it- and then Nagisa is sitting up with a grunt and forcing his face down onto his cock. Karma lets himself get pushed around like this for a while, letting Nagisa push his face on and off his cock, glistening with delight at the sounds of his breathy moans and groans. “Karma! Karm- _ ah _ , oh god, Karma, yes, faster,” his cute face is getting scrunched up. If he’d known just how delicious Nagisa would look like this, maybe Karma would’ve feasted earlier.

He pulls of Nagisa’s cock with a pop and smiles at him up from his vantage point. Nagisa’s face is red and flushed, and he’s never seen anything more erotic. He stands on shaky legs and allows Nagisa to take off his sweater and unbutton his shirt. 

Nagisa rolls a dusky nipple in his fingers and sucks the other one, letting Karma cry out and buck his hips into the table, desperate for friction. “ _Ah,_ Nagisa,” he grinds out between clenched teeth, a hand going down to skillfully remove the hair ties on Nagisa’s head, letting his long hair fall down like a curtain. It makes this entire gesture seem all the more wrong. Karma, big, strong, broad, Karma, letting small, petite, innocent Nagisa suck on his nipples in the darkness of their only school classroom, on top of Nakamura’s desk. He pushes Nagisa’s face away and slides his fingers into his mouth. 

“Suck,” Karma commands, his voice sinful. Nagisa runs his tongue up the underside of his two fingers, stopping to circle at the tip, hollowing out his cheeks and sucking. He continues this for a while as Karma undoes his own pants and underwear and drops them to the floor, letting them pool around his ankles as he’s too far gone to think about removing his shoes. His cock stands proudly at attention, a decent length and curving slightly upwards, a bead of pre-cum at the tip. Nagisa doesn’t really think much about it, he lets go of Karma’s fingers and bends his head down instead to lap at the head. “Fuck! Fu- _ ah _ \- fuck,” Karma shakes as Nagisa continues to run circles around his cock. 

In a burst of strength, Karma manages to pull out of Nagisa’s mouth and flip him around, so that Karma is facing his back. He slides one finger into Nagisa and gasps a little. He tries two, pushing in slowly, Nagisa writhing and panting out, “ah, ah ah!” 

“You’ve done this before,” Karma says, his voice full of wonder. “Tell me, Nagi _ sa _ , who did you think of when you did?”   


Nagisa pushes his hips back on Karma’s fingers as he starts to pull out. “You  _ slut _ ,” he says, voice rasping. He scissors the whimpering boy, brushing his fingers against his walls, and adds a third one. Nagisa grimaces slightly at the feeling, and Karma leans over him, covering his body completely and biting down hard on his neck. Nagisa says, “Karma!”

With fast reflexes, Karma lands a hand on his cock and squeezes tightly around the base, preventing him from coming. “Not yet, my viper,” he whispers as he pulls his fingers out and rubs the head of his cock over his hole. “How badly do you want me?”

Nagisa thrusts his hips back onto Karma’s cock. “Please, Karma, please just-”

“The best assassin in the class,” Karma presses into him slowly, unable to resist. “Reduced to a whimpering mess.”

Nagisa bucks and moans. “F-fuck, Karma,” he whimpers. They stay locked together for a heartbeat. “Move.” 

Karma does so with glee. He pushes in, and out, and then as fast as he can go, fucking into Nagisa hard and fast. Nagisa is moaning and meeting his every thrust, one hand snaking down to grip his cock and jerk it as fast as he can. “Harder, Karma,” Nagisa moans. “Fuck, Karma, Karma, Karma,” he chants his name like a mantra. When Karma tries a new angle, gripping Nagisa’s shoulder tightly and pulling him back, Nagisa clenches hard around him like he’d been burnt and all but shouts his name. 

Karma can’t take this. He pounds into Nagisa with a reckless abandon, squeaking the desk chairs and groaning low into Nagisa’s ear, “you’re so tight around me, Nagisa, fuck, you’re such a good boy for me.” As they near their climax, the words get progressively filthier. “Did you want to do this instead of fight? Ride my cock when you had your hands on me?”

Nagisa turns his head to look at him craning his neck. His hair has fallen flat on his face, and a thin sheen of sweat coats the red flush he’s worked up. His eyes are the slit pupils he gets when he’s incensed. Nagisa moans at the sight of a thoroughly fucked Karma and bucks into his hand.

“Gonna come, Karma,” Nagisa pants out. “Gonna-”

Karma lets go of his shoulders to grab a fistful of his hair. He yanks his head back by his hair and tugs on it. Nagisa moans like a bitch in heat.  

“Gonna come for me?” Karma asks, smiling serenely. “All over Nakamura’s desk? She’s going to sit there you know-”

His mind goes completely blank and his mouth drops open as he comes hard on the desk, coating it in stripes of white. He’s moaning, screaming, “Karma!”  

“Nn,” Karma groans and thrusts all the way into his now soft body. “You’re fucking hot,” he gets out, and then he’s coming into Nagisa, filling him up with his come. As though all his energy has left him with every spurt, he slumps over the table, grinning at Nagisa through sweaty bangs. 

“Hi,” Nagisa smiles at him. He leans forward and kisses Karma, slotting his tongue into his mouth and curling his hands into his hair. “Ah, look! Forty hits. Bitch-sensei was right.”

“You’re a beast,” Karma says tiredly, but kisses him again anyway.

**Author's Note:**

> Maybe I'll write fluff for them one day....


End file.
